732 DESCEIPTIVE GEOLOGY. 



stone comes in similar in, character to the Star Peak beds, from which one or 

 two indistinct fossils of the genera Ammonites and Rhynclionella have been 

 collected. Owing to the broken and deeply eroded state of the range, it is 

 impossible to arrive at the thickness of this limestone ; it probably, how- 

 ever, measures 1,000 feet. 



Conformably overlying it, directly south of Oreana, is a quite heavy 

 development of fine argillaceous slates, with .interstratified bands of calca- 

 reous shales and fine arenaceous beds, the series, however, being prevail- 

 ingly of very finely laminated argillites. They are without hesitation 

 referred to the Jurassic slates, so largely developed in Humboldt Canon. 



Where the Triassic strata pass under the rhy elites, east of Humboldt 

 Lake, they have a strike of about northeast true, and dip, so far as seen, to 

 the northwest. About the middle of the uplift, they are broken through 

 and overlaid by broad tables of basalt, which to a great extent mask the 

 structure. Southeast of Lovelock's Station, there is a rapid bend of the 

 entire formation into a north and south strike, with a dip to the west, which 

 continues for about 6 miles, when, to the east of Lovelock's Station, and 

 in the region of the little outcrop of Miocene strata, the whole body passes 

 again into a northeast strike, which continues for 5 or 6 miles, until the 

 range approaches the sharp valley dividing it from the northern end, where 

 they are turned off into a northwest strike. The dip through all this 

 region, with local exceptions, is toward the west, northwest, and southwest. 



In the crumpled country lying directly south of Oreana, embraced 

 between the dividing valley on the east and the Humboldt Valley on the 

 west, there is a local double fold in the limestones and slates, which does 

 not seem to penetrate deeply into the structure, the two half-folds upon 

 which the strata dip to the east being very shallow and limited. Besides 

 the folds, the strata are much disturbed by narrow dikes of vesicular 

 basalt, having a strike a few degrees east of north, and, so far as observed, 

 invariably dipping to the eastward. A peculiar feature of these basalts is 

 the large amount of calcite formed in the cells of this extremely porous 

 variety. 



Directly south of the Jurassic slates below Oreana, the range foot- 

 hills are occupied by an outburst of rhyolite, which continues north and 



